sample() function to create the create the numbers.
library(dplyr)
##
## Attaching package: 'dplyr'
## The following objects are masked from 'package:stats':
##
## filter, lag
## The following objects are masked from 'package:base':
##
## intersect, setdiff, setequal, union
fancy_matrix <-
sample(1:1000, 8*8, replace = TRUE) %>%
matrix(nrow = 8, ncol = 8)
fancy_matrix
## [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
## [1,] 773 315 438 470 556 77 362 103
## [2,] 73 992 896 290 715 366 448 725
## [3,] 389 997 123 673 258 942 963 37
## [4,] 332 378 210 458 637 455 123 203
## [5,] 497 296 597 383 641 766 192 320
## [6,] 998 931 936 572 947 678 172 606
## [7,] 708 801 494 601 543 331 900 630
## [8,] 21 602 77 467 299 83 460 160
raster() function can be fed with matrices to create a raster layer.
library(raster)
## Loading required package: sp
##
## Attaching package: 'raster'
## The following object is masked from 'package:dplyr':
##
## select
fancy_raster_layer <-
raster::raster(fancy_matrix)
raster::plot(fancy_raster_layer)
The raster() function can not only be used to create raster data on the fly, which is also not very interesting. Instead, we can use it to import already prepared to data.
.tiff files in the ./data/ folder of the workshop directory (repository). Do you get any warning messages?
getwd(). Setting is done with setwd().
immigrants_cologne <-
raster::raster("../data/immigrants_cologne.tif")
## Warning in showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj =
## prefer_proj): Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
# The warning message is due to the current transition of CRS definition
# systems. You can ignore it in this course.
+ and - operators.
# load all layers
immigrants_cologne <-
raster::raster("../data/immigrants_cologne.tif")
## Warning in showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj =
## prefer_proj): Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
germans_cologne <-
raster::raster("../data/germans_cologne.tif")
## Warning in showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj =
## prefer_proj): Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
inhabitants_cologne <-
raster::raster("../data/inhabitants_cologne.tif")
## Warning in showSRID(uprojargs, format = "PROJ", multiline = "NO", prefer_proj =
## prefer_proj): Discarded datum Unknown based on GRS80 ellipsoid in CRS definition
# create sum layer
immigrants_germans_sum <-
immigrants_cologne + germans_cologne
# create difference layer
difference_layer <-
inhabitants_cologne - immigrants_germans_sum
difference_layer
## class : RasterLayer
## dimensions : 289, 264, 76296 (nrow, ncol, ncell)
## resolution : 100, 100 (x, y)
## extent : 4094850, 4121250, 3084050, 3112950 (xmin, xmax, ymin, ymax)
## crs : +proj=laea +lat_0=52 +lon_0=10 +x_0=4321000 +y_0=3210000 +ellps=GRS80 +units=m +no_defs
## source : memory
## names : layer
## values : -2, 0 (min, max)
# get a summary statistic
summary(difference_layer)
## layer
## Min. -2
## 1st Qu. 0
## Median 0
## 3rd Qu. 0
## Max. 0
## NA's 62522
# create a table of counts
difference_layer %>%
as.data.frame() %>%
table()
## .
## -2 -1 0
## 11 2052 11711